Steam application system



June 23, 1970 c. D. sHELoR 3,516,607

STEAM APPLICATION SYSTEM Filed Aug. 2, 1968 1 N VEN TOR.

CLIFFORD D. SHELOR FIG. 4 3M 1 United States Patent O 3,516,607 STEAMAPPLICATION SYSTEM Clifford D. Shelor, Covington, Va., assignor toWestvaco Corporation, a corporation of Delaware Filed Aug. 2, 1968, Ser.No. 749,744 Int. Cl. Bb N24 US. Cl. 239-13 Claims ABSTRACT OF THEDISCLOSURE A steam application system for delivering dry steam to amoving paper web is formed with two chambers: a first, high pressure,high temperature chamber extending across the web and a series ofrelatively low temperature, low pressure chambers interconnected 'byvalves to the first chamber. Several conduits are positioned in thefirst chamber with their inlet ends connected to the second chamber andtheir outlet ends delivering steam to the web of paper. When hightemperature, high pressure steam is fed into the first chamber it passesthrough the valves into the second chambers and thence, through theconduits to the material being treated. Since the interior of the firstchamber and hence, the conduits, is at an appreciably higher temperaturethan the steam in the second chambers, any water entrained in the steamas it exits the second chambers is vaporized to give a substantially drysteam at the outlets of the conduits.

BACKGROUND OF THE INVENTION Field of the invention The treatment ofsteam in a steam application system to prevent moisture entrainment inthe steam jets; particularly at start up.

Description of the prior art In many manufacturing operations it isdesirable to apply dry steam to the material being treated. In the paperindustry, for example, steam may be applied to a moving web of paper asit is being manufactured to increase the rate of water removal from theweb, to modify calendering operations, etc. In processes of this type,it is desirable but difiicult to insure that the steam be substantiallydry and free from entrained moisture. This is particularly true wherethe nozzle is used on an intermittent basis; since, when the steamapplication unit is first turned on, any condensate which has collectedin the system is likely to be entrained in the initial burst of steamfrom the nozzle. One approach to solving this problem is shown in Pat.No. 2,838,982, wherein the steam orifices 25 are separated by 'a seriesof condensate drains positioned beneath the level of the orifices.

SUMMARY OF THE INVENTION A high pressure chamber extends across the webof paper or other material being treated, and serves as a manifold forseveral low pressure chambers positioned across the web. A series ofconduits extends from each low pressure chamber back through the highpressure chamber for directing steam from the low pressure chamber ontothe web. As the steam passes through the conduits any moisture entrainedtherein is flashed off, since the conduits are at a higher temperaturethan the steam entering them. It will be noted that this construction isparticularly suited for intermittent operation since, in the first fewseconds of operation the conduits are at the same temperature as thehigh pressure steam. Of course, after running a few seconds, atemperature gradient will be established between the interior and theexterior of the conduits and the temperature on the interior of the3,516,67 Patented June 23, 1970 conduits will then be somewhat less thanthe initial temperature. However, it will be substantially greater thanthat of the steam passing from the low pressure chamber and sufiicientto provide drying of the steam on a continuous basis. However, theadditional capacity that is available at each low pressure chamber as itis brought into operation provides an added advantage since it is atthis time that entrained moisture will most likely be encountered. Itwill also be noted that with the steam application system of the presentinvention the steam jets may be directed upwardly or downwardly or inany other direction without entraining moisture in the steam.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 of the drawings somewhatschematically shows the steam application system of the presentinvention as applied to a calendering operation;

FIG. 2 is an elevational view of the steam application system of thepresent invention;

FIG. 3 is a plan view of the apparatus of FIG. 2; and

FIG. 4 is a cross-sectional view taken on line 44 of FIG. 3.

DESCRIPTION OF A PREFERRED EMBODIMENT The present invention isparticularly adaptable for use in treating a paper Web with steam duringthe manufacture thereof. For example, steam might be applied at the wetend of a Fourdrinier machine to increase the water removal rate 'bysuctions, foils, table rolls and the like or steam might be applied justprior to the presses or dryers to increase the water removal rate atthese two sections of the papermaking machine. Additionally, dry steammight be applied to the web just prior to the calender to control thecaliper of the web leaving the calender stack. Thus, steam applied toselected areas transversely of the web would raise the temperature ofthose sections of the web, which in turn would raise the temperature ofthe corresponding portions transversely of the rolls of the calenderstack. The increase in temperature of the calender stack rolls wouldcause them to expand at that point and exert a greater pressing actionon the web passing therearound; thereby decreasing the caliper of thoseportions of the web to which heat was applied. For a more detaileddiscussion of this general subject reference is made to Pat. No.3,359,643. This type of operation is also shown somewhat schematicallyin FIG. 1 of the present drawings, wherein a paper web 1 is passed overa steam application system, referenced in its entirety by the numeral 2,and thence, around a series of rolls 3 of the calender stack to a winder4.

As seen in FIG. 2 of the drawings, the steam application system 2comprises a high temperature, high pressure chamber 5 having an inletconduit 6 and a condensate drain 7. Mounted on one wall of the chamber5, the bottom wall as seen in FIG. 2, are a series of low pressure, lowtemperature steam chambers 8. Each chamber 8 may be attached to thechamber 5 by means of a pair of depending studs 9 and, as seen in FIG.4, fluid communication between the chamber 5 and each chamber 8 isprovided by means of the air cylinder actuated valve members 10. Aseries of conduits 11 are mounted in the chamber 5 with their inlet ends12 extending inwardly into and in communication with a low pressurechamber 8 and their outlet ends 13 in communication With ambience.

In operation, high pressure, high temperature steam is admitted to thechamber 5 by means of the inlet conduit 6. From the chamber 5 the steampasses through the valves 10 into the chambers 8. As the steam passesthrough the valves 10 the pressure of the steam is reduced; therebyestablishing a pressure differential between the chambers and 8. Fromeach of the chambers 8 the steam passes out through the series ofconduits 11 to ambience, where it may be applied to, for example, amoving web of paper. Any condensate which may collect in the chamber 5will be drained off through the condensate drain 7 and, it will be notedfrom FIG. 4, the inlet ends of the valves may be positioned above thebottom wall 14 of the chamber 5 to prevent any of this condensate fromdraining into the lower chambers 8.

By maintaining a sufiicient pressure differential between the chambers 5and 8, the temperature in the upper chamber 5 maintains the conduits 11at a higher temperature than the steam in the lower chambers 8.Therefore, when the steam exits the chambers 8 through the conduits 11,its temperature is quickly increased, vaporizing any moisture entrainedwith the steam. While the pressure differential necessary to obtain thisresult will vary somewhat with the materials used and hence, the thermaltransfer characteristics of the system, in most cases it will be foundnecessary to have at least a 10 p.s.i. differential between the upperand lower chambers. While there does not appear to be a similarcriticality in the pressure differential between the inlet and outletends of the conduits 11, as a practical matter this differential in mostcases should be maintained at less than 1 p.s.i. In an actualinstallation, using mainly stainless steel components, a temperature andpressure in the chamber 5 of approximately 350 F. and 150 p.s.i.g. and atemperature and pressure in the chambers 8 of approximately 212 F. andless than 1 p.s.i.g., with the outlet ends of the conduits 11 atatmospheric conditions, were found to give satisfactory results.

In most instances when applying steam to a moving web of material, theamount of steam applied at the various positions across the web willvary. Therefore, the amount of steam admitted to each of the chambers 8from the chamber 5 may be controlled by means of a valve, as at 10, inresponse to varying conditions in the papermaking process. When aparticular chamber 8 is con tinuously receiving steam from the chamber 5a temperature gradiant will be established through the wall of theconduit 11. However, by selecting a high enough pressure differentialbetween the chambers S and 8 the temperature of the internal surfaces ofthe conduit 11 will be sufiicient to vaporize any moisture existing inthe steam as it exits the chamber 8.

A particular problem which exists, however, when a steam applicationsystem is used for intermittent operation is that moisture tends tocollect in the system when it is inactive. In this regard, it should benoted that with the steam application system of the present invention,when a particular chamber 8 is activated there is initially anadditional capacity for drying the steam exiting the chamber 8; sincethe conduits 11, while the chamber 8 is inactive, are allowed to reachthe full saturated temperature of the high pressure steam in the chamber5. Thus, additional capacity is provided exactly when it is needed most.

While the present invention has been described in conjunction with acalendering operation it should be noted that it is applicable to anyprocess where it is desired to apply steam. Additionally, it should befurther noted that although the steam application system has been shownand described with the high pressure, high temperature chamber mountedabove the low pressure chambers 8 and the jets from the outlets 13existing upwardly, the steam application system may be oriented in anydesired position; the only modification necessary being the relocationof the condensate drain 7.

It will be obvious that other modifications will occur to those skilledin the art within the scope of the appended claims.

What I claim is:

1. A method of distributing substantially dry steam comprising:

(a) directing steam to a first chamber,

(b) directing said steam from said first chamber to a second chamber,

(c) maintaining an appreciable pressure differential between said firstand second chambers, and

(d) redirecting said steam from said second chamber through said firstchamber to ambience.

2. The method of claim 1 wherein:

(a) said pressure differential between said first and second chambers ismaintained by reducing the pres sure of the steam in said first chamberas it is directed to said second chamber.

3. The method of claim 2 wherein:

(a) said pressure differential between said first and second chambers ismaintained at at least 10 p.s.i.

4. The method of claim 3 further comprising:

(a) maintaining a pressure differential between said second chamber andambience of less than one p.s.i.

5. The method of claim 4 further including:

(a) redirecting said steam from said second chamber through said firstchamber to substantially atmospheric conditions.

6. The method of claim 5 further comprising:

(a) removing condensate from said first chamber.

7. Apparatus for distributing substantially dry steam comprising:

(a) a first, high pressure chamber,

(b) a second, low pressure chamber,

(0) means establishing fluid communication between said first and secondchambers, and

(d) means for redirecting steam from said second chamber through saidfirst chamber to ambience.

8. The apparatus of claim 7 wherein:

(a) said redirecting means comprises conduit means mounted in said firstchamber and establishing fluid communication between said second chamberand ambience.

9. The apparatus of claim 8 wherein:

(a) said means for establishing fluid communication between said firstand second chambers comprises valve means interconnecting said twochambers.

10. The apparatus of claim 9 further comprising:

(a) a series of openings defined in a wall of said first chamber,

(b) a series of openings defined in a wall of said second chamber,

(c) said conduit means having inlet and outlet ends,

(d) the inlet ends of said conduit means being positioned in saidopenings in said second chamber,

(e) the outlet ends of said conduits being positioned in said openingsin said first chamber,

(f) means for supplying steam to said first chamber,

and

(g) means for removing condensate from said first chamber.

References Cited UNITED STATES PATENTS 4/1921 Flint 34-155 3/1949 Dawson34155 6/1958 Dupasquier 34160 X 6/1962 Dupasquier 34-155 X M. HENSONWOOD, JR., Primary Examiner I. I. LOVE, Assistant Examiner US. Cl. X.R.

